United face the Spanish side at the Ramon Sanchez Pizjuan in their Champions League last 16, first leg match on Wednesday night.

Pogba, who missed the weekend win over Huddersfield due to illness, had been expected to return to the starting XI.

But the £89million man has been left out of the lineup, with Ander Herrera, Nemanja Matic and youngster Scott McTominay being picked in a midfield trio.

The Portuguese has spoken to BT Sport, telling them his reason behind the Frenchman’s omittance.

Pogba's on the bench (Image: Getty Images Europe)

Scott McTominay gets the nod (Image: Getty Images Europe)

"You always go to the one who doesn’t start. Scott McTominay is working hard every day, he is feeling good and strong,” said Mourinho.

“He played the last match for 90 minutes and Paul last Saturday wasn’t able to play, and this is the kind of game where I think a player must feel 100 per cent.

"Paul gave us some doubts by not playing last Saturday, by his own decision, he was not feeling good."

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When Mourinho was pushed further on Pogba, he said: "Three questions on Paul, you have no others? Ask another one."

Pogba's omission from the starting line-up will cast further doubt on his Old Trafford future, with the France international having been subbed in two of his last three games for United and dropped in the other.